DELRAY BEACH, Fla. — Not far from the beach, Representative Allen B. West recited the Declaration of Independence at a sweltering Fourth of July fair, lobbing the sentences into the crowd and hoping the gravitas of the words would sink in.

Mr. West, a Republican positioned near the top of the Democrats’ knockout list, is fond of letting words speak for themselves — no parsing, no apologizing, no backtracking. In this era of survey-tested language, he is a verbal street brawler, unflinching in his speech, a trait that has won him the adulation (and the campaign contributions) of conservatives and Tea Party supporters who cheer on his every Westism. He is one of the top fund-raisers among House Republicans, rivaling Speaker John A. Boehner.

“People are looking for leadership,” said Mr. West, 51, a first-term congressman, in a brief interview as supporters posed for photographs and exchanged a few words. “Principles, pragmatism, passion and leadership: It’s obvious we are representing those values.”

Despite his celebrity and prodigious fund-raising, Mr. West, who announced he would run in a new district this year, faces a serious challenge in November. The question for Democrats is this: Will Mr. West’s conservative stance and unbridled style pass muster with a new set of Florida voters in a swing district that is evenly split? In that race, Mr. West is likely to face Patrick Murphy, 30, a Democrat and political neophyte who is shaping up to be a potent force.

Democrats are banking that in a presidential election year, Mr. West will fail to sway enough independent-minded voters to win in November. They view the newly created 18th Congressional District on the Treasure Coast as one of six possible Democratic gains in Florida. Impressed with Mr. Murphy’s fund-raising, the Democratic Congressional Campaign Committee has put its financial and organizational strength behind him.

Aubrey Jewett, a political science professor at the University of Central Florida, said the race would hinge largely on turnout. At the moment, President Obama and Mitt Romney, the presumptive Republican nominee, are neck-and-neck in Florida.

As for Mr. West’s penchant for controversy and his conservative voting record, it is too early to gauge its impact on the race. But he runs the risk of turning off at least some potential voters at a time when the Tea Party’s influence in Florida has encountered a backlash, said Kevin Wagner, a political science professor at Florida Atlantic University.

Professor Jewett said, “The danger for West is appearing that he is more interested in headlines and bombast and not as interested in representing voters in the district in a solid conventional way.” He added: “When he won two years ago, he seemed like a breath of fresh air to a lot of the voters down there who were anxious to send a message that they were dissatisfied with President Obama. Now that he has been in office for two years, his act may be wearing a little thin.”

Both candidates face primary opponents but are expected to win the races handily.

This year, Mr. West learned that with a squiggle here and a slash there, his original Congressional district in Broward and Palm Beach Counties had become far less hospitable to conservative Republicans. He jumped a step north, declaring he would run in a new swing district encompassing St. Lucie County, Martin County and a slice of northern Palm Beach County.

Mr. Murphy, who was intent on defeating Mr. West, also shuffled north and rechallenged him. The newly drawn 18th Congressional District voted for Mr. Obama in 2008 and for Alex Sink, the Democrat who ran unsuccessfully for governor, in 2010. In 2004, George W. Bush won with 51 percent.

Campaign handicappers have said that Mr. West is trying to modulate his tone; his first campaign ad, while staying true to his views, is sedate by his standards.

But Mr. West, who is fond of holding town hall meetings, said that while he is plunging into local issues, his principles are unshaken and portable. “Why would you change your principles?” he said. “They fit in no matter where.”

Bill Paterson, the chairman of the Republican Party in St. Lucie County, where there are more Democrats than Republicans, said Mr. West would have little trouble hooking Republicans in that county. Mr. West, a retired Army officer, has a conservative voting record but has sometimes broken from the party line.

“So many people want a breath of fresh air,” Mr. Paterson said. “He is going to tell you the truth, whether you like it or not. His message doesn’t change based on the group he is talking to.”

In his whirlwind first term as a congressman and one of only two black Republicans in the House, Mr. West has said flat-out that as many as 80 House Democrats are Communists. He has remarked that the Democratic Party would do the Nazi propaganda minister Joseph Goebbels proud with its use of “lies and deceits.” He has called people with Obama bumper stickers a “threat to the gene pool.” Recently, he said that President Obama wants Americans “to be his slave and be economically dependent on him.”

Later, on Fox News, he said the rise in the number of people on Social Security disability since 2009 merely stokes economic dependency, “which, to me, is a form of modern, 21st-century slavery.” Mindful that Mr. West’s new district is teeming with retirees, Democrats delighted in hearing the words “Social Security” and “slavery” in the same sentence and quickly publicized it.

His words, no matter how raw, steer donations his way from around the country. He raised $2.2 million for the quarter, one of the highest tallies in the country, and has $3.7 million on hand.

This election cycle, he has raised nearly $10 million, a huge number for the House. Mr. Murphy raised more than $500,000 this quarter and $2.2 million so far this election cycle; he has nearly $1.3 million on hand.

As for the race, Mr. West’s campaign has described Mr. Murphy as a cookie-cutter Democrat with little experience.

“At this point in time, Murphy is running a negative campaign to raise liberal money,” said Tim Edson, Mr. West’s campaign manager. “No issues. No substance. Just negative attacks.”

It is true that Mr. Murphy has tapped into voters who strongly dislike Mr. West. An accountant who graduated from the University of Miami, Mr. Murphy is vice president of Coastal Environmental Services, which specializes in disaster relief and environmental cleanup, including the BP oil spill. The company is affiliated with a large construction company run by his family.

“There are people saying, ‘I don’t care who you are, but you are better than Allen West,’ ” he said. “It’s truly a moderate district.”

Mr. Murphy, a Florida native, said he decided to challenge Mr. West because he was angry about the partisan gridlock in Washington. Mr. West, he said, epitomizes the bottleneck.

“It’s about getting something done,” said Mr. Murphy, who calls himself progressive on social issues and more moderate on fiscal issues. “The first thing I want to do when I get to Congress is have dinner with a Republican.”

A version of this article appears in print on July 20, 2012, on page A13 of the New York edition with the headline: G.O.P. Firebrand Faces Election Challenge in a New Swing District in Florida. Order Reprints|Today's Paper|Subscribe